Know your place values. People get these wrong way more often than college-bound almost-adults should.
Turning a Fraction into a Decimal
If you need to turn a fraction into a decimal, simply think of it as the top (the numerator) falling to the right "under the bridge." So becomes . If you're typing it into your calculator, simply read the fraction as written, that is "5 divided by 8" and that's what you type in.
Turning a Decimal into a Fraction
If you need to turn a decimal into a fraction, it's even simpler. The denominator is given to you in the place value. The number .024 is read as twenty-four thousandths, right?
24
---------
1000
Done.
But what about reducing, you might ask?
-Hint: Remember, on the SAT grid-ins, you DO NOT need to reduce unless the answer you got doesn't fit into the bubbles.
But that doesn't help me with
24
---------
1000
! you might shout in frustration.
-Hint: If you have a graphing calculator, use the MATH button. On most models, if you hit the MATH key, a list comes up that starts with "Frac" Type .024 (the original decimal we were working with) into your calculator. Hit MATH. Select Frac and hit Enter. What do you get? The reduced fraction 3/125. The Frac button is awesome.
-Trick to Watch Out For: Keep in mind, especially on the SAT grid-ins, the answer can be either a fraction or a decimal. Even if the question was phrased in fraction form, if you get .2 as an answer, grid it! And move on. On the multiple choice questions, if you get a fraction and the answers are in decimals, or vice versa, type the fraction into the calculator to get the decimal or use the Frac button to quickly convert your answer to the form they prefer.
Decimal Fraction Equivalents
Despite the awesome Frac button, it's good to have the more common decimal/fraction equivalents memorized. And if you don't have a Frac button, you'll definitely need these.
1
---------
10
.1
1
---------
4
.25
1
---------
3
.3
1
---------
5
.2
1
---------
2
.5
2
---------
3
.6
3
---------
4
.75
-Hint:
1
---------
3
, when typed into your calculator, will give you .33333333. If you need to manipulate that fraction, like multiply it to another number or something, type in (1/3) and leave that long decimal when you hit your next operation so that your screen reads "Ans *..." This is especially important with
2
---------
3
. Your calculator will round (2/3) to .66666667, but will keep in its memory that it's actually a repeating decimal. If you decide to simply enter ".67" and then proceed to multiply, you may get an answer that's off - for example:
A question states
2
---------
3
x = 2.
You decide to divide by
2
---------
3
on each side to isolate the x, but first you decide to find the decimal of
2
---------
3
to make it easier, a wise strategy. You type it in and get .66666667, which you round to .67 in order to do the division. So you type in "2/.67" You will get 2.9850746, an answer that is not one of the answer choices. Try the same problem on your own right now, using .6667 for
2
---------
3
.
2.99985.
Now try typing in "2/(2/3)" What do you get?
3, which is the answer we wanted. If you know that this is happening and you get 2.9850746 and all the answers are integers and 3 is one of the choices, sure, you could guess and choose that one, but that's a dangerous habit to get into. Don't round and don't play with numbers. Just be careful.
becomes 
. If you're typing it into your calculator, simply read the fraction as written, that is "5 divided by 8" and that's what you type in. 
Frac" Type .024 (the original decimal we were working with) into your calculator. Hit MATH. Select 
